Root cause of the "grid escapes the window when scrolled" bug: UiElement.
DrawSelfAndChildren runs ApplyAnchor on every child AFTER OnDraw, which captured
each cell's scroll-0 position and reset Top to it every frame, fighting
LayoutCells' scroll offset. Cells are laid out procedurally by the list, so they
must be exempt — AddItem now sets cell.Anchors = None, making LayoutCells the
sole authority. Regression test reproduces the anchor-pass interaction (the unit
tests missed it by calling LayoutCells in isolation, never the draw traversal).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
OnEvent handles the Scroll wheel in grid mode (mirrors UiText's sign), driving
the shared UiScrollable. The bound gutter scrollbar (next task) is the primary
scroll affordance; the wheel is the convenience path.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Grid mode now drives a shared UiScrollable from its content + clips whole rows
to the panel (cells offset by -ScrollY, Visible toggled by whole-row clip,
mirroring UiText). Fill mode (toolbar single cell) unchanged. LayoutCells made
internal for tests; RowCount helper added.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Columns + CellWidth/CellHeight + a row-major CellOffset/LayoutCells pass.
CellWidth<=0 keeps the single-cell fill mode (toolbar slot sizes to the
list — unchanged); CellWidth>0 tiles cells in a grid. Layout runs on
AddItem and per-frame in OnDraw so a list resize reflows.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Ports retail UIElement_ItemList (class 0x10000031) as a behavioral-leaf
container that owns its UiItemSlot children procedurally. Single-cell
default covers every toolbar slot; N-cell grid is deferred to the inventory
phase. OnDraw syncs the cell rect to the list's Width/Height each frame so
the cell is sized and hit-testable from the first rendered frame, even
though the factory sets rect AFTER construction.
Factory: adds `0x10000031u => new UiItemList(resolve)` arm before the
fallback, so all 18 toolbar itemlist slots route to UiItemList instead of
UiDatElement.
Tests: 4 new (IsLeafWidget, StartsWithOneCell, Cell_returnsFirstSlot,
Create_buildsUiItemList_forItemListClassId). All 4 pass; full suite green
(415 pass / 2 skip in App.Tests; 0 fail total).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
